Corrosion of common secondary tubes
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Leaks frequently occur in the pump pipeline leading from the secondary stripping tower in my facility; the leakage points are all due to pitting corrosion in the straight sections of the pipeline. The pipeline was made of 1CR5MO material, and leaks occurred after 2.5 years of use; it was then replaced with 316L material, but leaks still occurred after half a year of use. The acidity of the liquid is around 30, sulfur content is 0.4%, and chloride ions are less than 0.5 ppm. The material of the pump’s outlet pipeline is the same as that of the inlet, but no leakage has occurred. Experts, please analyze the reason.
This post was last edited by lovepds on 2017-1-17 11:19. What’s the temperature? What is the flow rate of the pipeline? Is the acid value 30, with the unit being mgKOH/g? Is there a pipe layout diagram?
Try doing a side-line iron ion test, and also inject a high-temperature corrosion inhibitor into the middle section for recirculation
The secondary line temperature is around 275, the flow rate is 0.73 m/s, and the acidity is 30 units of mg·KOH/100ml
The secondary line temperature is around 275, the flow rate is 0.73 m/s, and the acidity is 30 units of mg·KOH/100ml
The area where it’s missing might be the area where the dew point is present
The acid value is not high, nor is the flow rate high; it’s pitting corrosion, and theoretically it’s not caused by naphthenic acid corrosion. It must be caused by some other factor; I’m not sure if the layout of the pipes is related to it. Severe local erosion may have accelerated the corrosion caused by naphthenic acids Is it the location of this gas-liquid phase transition that causes more severe erosion? It’s all just speculation; it’s better to take the location of corrosion to a corrosion monitoring agency for testing
Consider the possibility of dew point corrosion in ammonium salts.
The distillation outlet temperature on the secondary line isn’t very high. If the pipeline leading from the bottom of the stripping tower to the pump is prone to leaks, then it’s necessary to check whether there is erosion caused by turbulent flow. Since the pipeline has been replaced many times, the material used shouldn’t be the main issue. Try adjusting the distillation outlet temperature and see if that helps
On our end, there is severe top reduction, secondary pumping issues, and secondary water-cooling corrosion; especially the pumping operations need to be done almost once a year. At present, the highest-grade material used is stainless steel